Field of the Invention
The present invention relates generally to electrically operated door access systems in which the door is either unlocked or opened, or both unlocked and opened, by accessing an electronic control system, and more particularly to an improved pressure-actuated door access bar which may be located on a door through which access is controlled by the electrically operated door access system, whereby the pressure-actuated door access bar is used to trigger unlocking or opening, or both unlocking and opening, of the door following pressure being exerted on the pressure-actuated door access bar by an individual desiring access or egress through the door.
Hardware and systems for controlling egress and access through doors may predominantly be classified into one of two categories. The first category is that of hardware and systems which are designed to limit and control egress and access through doors. Devices falling into this classification are generally utilized for theft-prevention or to establish a secured area into which (or from which) entry is limited. The second category is that of hardware and systems which are designed to facilitate access through doors by opening the doors in a manner not requiring great strength or facility by the person desiring access. Devices falling into this second classification are used to automate the opening of a door in an easy, yet controlled, manner suitable for use by handicapped individuals, for example.
The first of these two categories includes controlled access security doors and operating systems for such doors. Such doors and systems have evolved over the years from simple doors having heavy duty mechanical locks thereon to sophisticated egress and access control devices. In bygone times, heavy duty chains and locks were the norm on security doors which were not generally used, or which were used to prevent theft or vandalism. However, fire codes have made such relatively simple door locking systems obsolete, at least in most developed countries. Emergency exit doors are required by law to be provided in all commercial buildings, and such doors must be operative in the event of a fire, earthquake, or other emergency.
These exit doors are typically provided with heavy horizontal push bars, which unlock the door upon actuation and which may provide an alarm of some sort. The early alarms on such doors were either mechanical in nature, such as wind-up alarms contained on the push bar mechanism, or completely separate electrical circuits actuated by a switch opened as the door was opened. Accordingly, egress from such doors was immediate, and, although egress was accompanied by an alarm, typically the person leaving through the door was long gone by the time security personnel arrived.
Many stores suffer great losses through emergency doors, with thieves escaping cleanly through the emergency doors with valuable merchandise. In addition, industrial companies also suffer pilferage of valuable equipment and merchandise through such emergency exit doors. While one solution is to have a greater number of security personnel patrolling the emergency exit doors, to do so is also an expensive solution.
As might be expected, the art reflects a number of emergency exit access activation devices which attempt to solve this problem. A first type of device is found in U.S. Pat. No. 4,257,631, to Logan, Jr., which describes a system activated by a push bar which, upon depression, moves a switch carried by the door to sound an alarm and start a timer delay. After the delay, the door is unlocked.
This type of device in which a push bar containing an electrical switch therein is used to initiate a request for access or egress is by far the most common. It has not always been viewed as the optimum solution, however, due to the difficulty in making it durable and long lasting in addition to being relatively simple and inexpensive. Several other types of systems have been proposed, and, although none of these systems has found great acceptance, a brief discussion of them is in order.
U.S. Pat. No. 4,328,985 and U.S. Pat. No. 4,354,699, both also to Logan, teach a hydraulic system for accomplishing the delay prior to unlocking the door, and a retrofit locking device of the same type which is usable with any door latching system, respectively. These two systems are thus mechanical rather than electrical in nature.
U.S. Pat. No. 4,652,028 and U.S. Pat. No. 4,720,128, to Logan et al. and to Logan, Jr., et al., respectively, teach an electromagnet mounted on a door jamb, an armature on the door held by the electromagnet to retain the door in the closed position, and a switch mounted near the electromagnet which is used to indicate when the door is being opened or tampered with. The Logan, Jr. et al. '128 patent also adds a set of contacts to confirm that the armature properly contacts the electromagnet. These systems have no switch located in a door access bar.
As mentioned above, the second category of hardware and systems includes devices and systems which are designed to facilitate access through doors by opening the doors in a manner not requiring great strength or facility by the person desiring access. One example of such a device is the type of door commonly found in supermarkets, which is typically radar controlled. Another example is a power actuated door in a hospital corridor, wherein when a wall switch is depressed the door automatically opens.
Both of the two categories of devices discussed above are beneficial, yet both categories of devices still possess several disadvantages and are illustrative of problems inherent in the art. For example, the preferred type of door access bar, the type containing an electrical switch therein, has several disadvantages. First, in order for the switching mechanism to operate, there must be a minimal amount of free movement in the bar. The use of a limit switch in the bar requires the switch to be precisely adjusted to operate properly. In addition, one or more springs must be utilized in order to keep the switches in the open position when the door access bar is not being depressed. In addition, typical electrical switch type door access bars are mechanically fairly complex, and are not inexpensive to manufacture.
A substantially improved door access bar is illustrated in U.S. Pat. No. 5,564,228, to Geringer et al. The improved door access bar of the Geringer et al. '228 patent contains an electromechanical mechanism through which mechanical contact by a user with the door access bar is translated into an electrical output, which may be utilized to initiate the process of unlocking the door on which the door access bar is mounted. The transducer used by the door access bar of the Geringer et al. '228 patent is a force sensing resistor (FSR), which has a resistance which drops when a compressive force exerted across the force sensing resistor increases.
The FSR transducer is placed in series with a reference resistor having a fixed resistance, with a constant voltage being placed across the FSR and the reference resistor. As an increasing amount of force is applied to the FSR, its resistance drops, leaving a larger portion of the voltage across the reference resistor. A comparator having a predetermined reference voltage provides an electrical output when a predetermined amount of force is applied to the door access bar, with the electrical output from the comparator being used to open the door. The amount of force needed to be applied to the sensor bar to trigger an output from the comparator may be adjusted by varying the reference voltage.
The door access bar of the Geringer et al. '228 patent contained two FSR's, one mounted in the door mounting hardware located at each end of the door access bar. When the predetermined pressure was exerted on either FSR, the circuitry of the Geringer et al. '228 patent caused the door to be opened. The door access bar of the Geringer et al. '228 patent represented a substantial improvement over the prior art, and has met with considerable commercial success, and U.S. Pat. No. 5,564,228, to Geringer et al., is hereby incorporated herein by reference.
The use of the door access bar of the Geringer et al. '228 patent on a large number of doors has presented a rather unusual problem which may cause unintended switching operation of the door access bar. When the door access bar of the Geringer et al. '228 patent is mounted on a door which is warped, or which becomes warped after the door access bar is mounted thereon, a slight twisting in one of the mounting members of the door access bar may exert pressure on one of the FSR's, causing the door to unlock. This results in a service call in which the door access bar must be recalibrated to compensate for the increased pressure on the FSR. In some extreme situations, the door will become warped to such an extent that the door access bar will no longer properly operate. The same problem presents itself in the case of sagging doors, as well as in tweaked glass stiles.
Accordingly, it is accordingly the primary objective of the present invention that it present a door access bar having an improved mounting arrangement for electromechanical force transducers through which mechanical contact by a user with the door access bar is translated into an electrical output which may be utilized to initiate the process of unlocking the door on which the door access bar is located. It is a directly related objective of the door access bar of the present invention that it contain the electromechanical force transducers entirely within the door access bar itself, and not between the door access bar and its mounting mechanism, thereby obviating inappropriate force sensing problems associated with warping or sagging of the door the door access bar is mounted on. It is another objective of the door access bar of the present invention that it have redundant electromechanical force transducers to ensure that pressure exerted on the door access bar is reliably sensed, with either force sensor being sufficient to trigger operation of the door access bar to cause the door to be unlocked and/or opened.
It is a further objective of the door access bar of the present invention that it require only a slight degree of force and minimal movement of the door access bar to initiate the electrical output indicating a desire for access or egress, and that the minimum amount of force required to initiate opening of the door be fully adjustable over an appreciable range. It is still another objective of the door access bar of the present invention that it include an emergency override switch which will operate to open the door even if both of the electromechanical force transducers or the control circuitry were to fail. It is a related objective of the door access bar of the present invention that the emergency override switch be operated by the same motion exerted on the door access bar that normally causes the electromechanical force transducers to unlock and/or open the door. It is yet another objective of the door access bar of the present invention that it be both easy and quick to mount on any door or other desired location.
The door access bar of the present invention must be of a construction which is both durable and long lasting, and it should also require little or no maintenance to be provided by the user throughout its operating lifetime. In order to enhance the market appeal of the door access bar of the present invention, it should also be of inexpensive construction to thereby afford it the broadest possible market. Finally, it is also an objective that all of the aforesaid advantages and objectives of the apparatus of the door access bar of the present invention be achieved without incurring any substantial relative disadvantage.